1. Field of the Invention
The present invention relates to a subject estimating method and a subject estimating device for estimating a subject which is a structure such as a building and a landscape, included in an image. The present invention also relates to a program for causing a computer to execute the subject estimating method.
2. Description of the Related Art
Conventionally, image data obtained by reading out an image recorded on a negative film or image data obtained using a digital camera are organized and stored. However, as the amount of the image data increases, the more troublesome organization work of the image data becomes. Especially, in a case that the image data are obtained using the digital camera which requires no film cost, there is a tendency that a large amount of image data is obtained. As a result, the organization work of the image data becomes extremely troublesome. Therefore, various methods have been proposed wherein the image data are automatically sorted, such as a method of sorting the image data for every medium in which the image data are recorded or for every film from which the image data are obtained and a method of sorting the image data into hierarchical folders for every year/month/day. A method has also been proposed wherein photography date/time information representing a date/time of photography and photography place information representing a place of photography are associated with image data obtained by photography and the image data are sorted based on the photography date/time information and the photography place information (refer to Japanese Unexamined Patent Publication No. 2001-228528). By using these methods of automatically sorting the image data, a user can efficiently organize the image data.
Meanwhile, in a case that image data are sorted, if a subject such as a building and a landscape, included in an image represented by the image data can be recognized, the image data can be sorted according to the subject included in the image. Therefore, a method has been proposed wherein: a sightseeing area is specified based on photography place information; an image of a mountain or a lake in the sightseeing area is retrieved as a reference image; and a composite image is printed by combining the reference image with an image obtained in the sightseeing area (refer to paragraph 0099 in Japanese Unexamined Patent Publication No. 2001-36842). According to this method, it is possible to know in which sightseeing area the image has been obtained by glancing at the composite image. Therefore, the image data can be easily organized.
However, in the method described in Japanese Unexamined Patent Publication No. 2001-36842, the composite image is created by combining a predetermined reference image of the sightseeing area with the obtained image. Therefore, there is a risk that a structure such as a building and a landscape, which is not included in the obtained image is combined with the obtained image.
Meanwhile, if correlation values between a plurality of structure images such as the building and the landscape and the image represented by the image data are obtained, and a structure with the highest correlation value included in a structure image is estimated to be a subject included in the image represented by the image data, only the structure included in the obtained image can be associated with the obtained image. However, since a number of the structures such as the building and the landscape is huge, if correlation values between all of the structure images and the image represented by the image data are calculated, it requires a long time to estimate the subject.